In addition to conventional ground broadcasting, satellite broadcasting services using broadcasting satellites (BS) and communication satellites (CS) are currently in use. Television sets with a converter to receive such satellite broadcasting are available on the market, but since that the number of such channels is increasing, there is a need for useful broadcasting channel selection.
For the ground broadcasting, on the other hand, the second generation EDTV broadcasting is under study. The aspect ratio of the TV broadcasted images is changing from the current ratio of 4:3 to the wide aspect ratio of 16:9 while maintaining compatibility with the current broadcasting. Television sets for the second generation EDTV broadcasting are designed to maintain the compatibility with the conventional images. Specifically, when displaying an image with the aspect ratio of 4:3 on a display unit for the aspect ratio of 16:9, the image is compressed in the horizontal direction so that the 4:3 image can be displayed on the 16:9 screen.
Some inventions have disclosed using a blank part on the screen generated by compression when a television set for the wide aspect ratio receives the ground and satellite broadcasting, proposing that such blank parts be used for broadcasting channel selection as described above.
One of such proposals is disclosed in Published Unexamined Japan Patent Application No. 62-263781 (No. 263781/1987). This application discloses a television set which displays images of other channels and high definition TV images in the blank part of the screen. By displaying, images of many broadcasting, stations other than the selected one at the same time, this television set provides a useful advantage for channel selection to the user.
A known television set having two tuners which uses one tuner to display images from the selected broadcasting station and the other tuner to repetitively select channels one by one so that images from a plurality of stations can be displayed at the same time as reduced images on the display unit. Thus, the image displayed on the screen can be quickly switched between the images based on both tuners (Refer to Published Unexamined Japan Patent Application No. 6-54269 (No. 54269/1994)).
Another invention proposes a television set having two divisional screens which displays reduced images (search screen) from various stations on one of the screens [Refer to Published Unexamined Japan Patent Application No. 8-223495 (No. 223495/1996) (Japan Patent Application No. 7-30880 (No. 30880/1995))].
With such configuration, the user can check the reduced images from various stations to select a channel and immediately display the selected image on the main screen.
With an increasing numbered channels, however, there is a problem that such television set cannot display all channels to be watched. Therefore, the search screen is designed to allow switching as shown in FIGS. 7(a) and (b). Specifically, after searching Channels 1 to 9 as shown in FIG. 7(a), the search screen is switched to the next screen displaying Channels 10 to 18 for searching as shown in FIG. 7(b).
In the above case, a two-screen displaying television set with the main screen on the left and the sub-screen on the right is provided with a function to display nine reduced images on the sub-screen as the search screen for the broadcasting waves which is received as input signals to the antenna. It has a memory for each of these nine images and the video data channel-searched and selected by the tuner is stored on the memory for later displaying on the screen. Naturally, they are still pictures. It has nine small screens only and, if there are ten or more broadcasting stations, it is necessary to switch to the next set of small screens. The data on the memories are updated by searching again upon completion of the nine small screens, searching so that the image is switched to a new one.
Though this configuration can display all channels on the search screen, it cannot display all channel data on a single screen. It is always necessary to follow a troublesome operation procedure to switch between screens.
Therefore, it is an object of the present invention to provide a television set which can display all channels desired or frequently used by the user on one screen to as the search screen.